I am developing a CMS and I have a category class like this :
public partial class Category
{
public int CategoryId {get;set;}
public string CategoryName {get;set;}
public string CategoryType {get;set;}
}
I am using Entity Framework to store & create such database table in my database. Now, how can I add dynamic fields to this model and hence to the database. I am allowing the user to add his desired custom fields to be added.
So, my database schema becomes
Category(CategoryId, CategoryName, CategoryType, CustomField1, CustomField2);
How can I do this using EF 5?
You can't in the way you expect it. Instead of adding custom fields to Category table you need something like CategoryExtension table where you will store CategoryId, FieldName and FieldValue (key-value pairs related to specific category record) where CategoryId will be FK to Category table and for example CategoryId and FieldName will build composite PK. Your classes will then look like:
public partial class Category
{
public int CategoryId {get;set;}
public string CategoryName {get;set;}
public string CategoryType {get;set;}
public virtual ICollection<CategoryExtension> Extensions { get; set; }
}
public class CategoryExtension
{
public int CategoryId { get; set; }
public string Name { get; set; }
public string Value { get; set; }
}
Related
I created a code first project in which there is a post model and person model:
public class post
{
[Key]
public int postId { get; set; }
public string title { get; set; }
public virtual person sender { get; set; }
}
public class person
{
[Key]
public int personId { get; set; }
public string name { get; set; }
}
I want to create a post, in which sender persons' info exists but person is defined as an object. How can I insert an existing person to a post when I create a new post? Actually I can only insert some fields like int, string etc. by taking value from views but in this case it is not a value it is an object, how can I insert the data?
e.g.
code:
ViewBag.personlist = new SelectList(db.persons,"personId","name");
view:
#Html.DropDownListFor(model => model.sender, (SelectList)ViewBag.personlist, "select item")
In database there is no sender item but person_postId, because of this reason dropdownlistfor send NULL value, how can I deal with that?
If I understand what you want correctly, you need to add the personID foreign key to your post model:
public class post
{
[Key]
public int postId { get; set; }
public int personId { get; set; }
public string title { get; set; }
public virtual person sender { get; set; }
}
As it stands you have a navigation property but no foreign key to associate the post with a person. The following line:
public virtual person sender { get; set; }
sets your navigation property, however it needs an personID from the person model to be a field in the post model so that there is a recorded link between that person and the post. Entity Framework will automatically label personID as a foreign key by virtue of having the navigation property set.
I have a contact class
[Table("Contacts")]
public class Contact
{
public string Id { get; set; }
public string Name { get; set; }
}
I have two classes inheriting from Contact:
[Table("Employees")]
public class Employee : Contact
{
public decimal Salary { get; set; }
}
[Table("Suppliers")]
public class Supplier : Contact
{
public string TIN { get; set; }
}
I am using Entity Framework 6.3 as my ORM.
Can I model something where the same contact can be both Employee and
Supplier with the same unique Id.
Employee emp = new Employee();
emp.Id = "C1";
emp.Name = "Employees";
emp.Salary = 10000;
emp.TrackingState = TrackingState.Added;
Supplier sup = new Supplier();
sup.Id = "C1";
sup.Name = "Employees";
sup.TIN = "ABC";
sup.TrackingState = TrackingState.Added;
When I do:
context.Employee.Add(emp);
context.Supplier.Add(sup);
context.Save();
Obviously, it will not allow me to add the record.
I get an error:
"Violation of PRIMARY KEY constraint 'PK_dbo.Contacts'. Cannot insert duplicate key in object 'dbo.Contacts'. The duplicate key value is (C1).\r\nThe statement has been terminated."
Can I make the Supplier also share the same Id as that of employee and
enable insert / update of employee and supplier?
Thanks
I assume you are not doing any specific inheritance mapping which by default will map this as Table per Hierarchy (TPH) inheritance. With this mapping you get a single Db table that contains the aggregate of all the fields in the base type and the dependent types with a discriminator field to know which type the row should be materialized. This allows for doing a query where you ask for a type.
With TPH each row can only be a single type, so you can not have the same row be both an Employee and Supplier.
There is another type of mapping you can do called Table Per Type (TPT) which will create a table for each type, so in your case 3, one for the shared fields, and one for each dependent type. This should allow for what you are asking about. (YMMV)
However, it seems to be that Employee and Supplier would be used in much different domains so I would suggest that you create your Contact table and relate it to both your employee and supplier.
[Table("Contacts")]
public class Contact
{
public string Id { get; set; }
public string Name { get; set; }
}
[Table("Employees")]
public class Employee
{
public string Id { get; set; }
public string ContactId { get; set; }
public decimal Salary { get; set; }
public Contact Contact { get; set; }
}
[Table("Suppliers")]
public class Supplier
{
public string Id { get; set; }
public string ContactId { get; set; }
public string TIN { get; set; }
public Contact Contact { get; set; }
}
Now you can query for an employee:
db.Employees.Include(e => e.Contact).First();
Or for a Supplier:
db.Employees.Include(e => e.Contact).First();
Which might be cleaner than the inheritence query you would need:
db.Contacts.OfType<Employee>().First();
In both the Has A modeling I show above and the Is A Modeling with TPT you are getting three tables. You just have the FK in what I show rather than the same ID in 3 tables with TPT.
There is also Table Per Class you can look at, which is similar to TPT but you don't get a table for the abstract/parent class, rather you get table for each dependent type with all the fields in it. I don't think this is what you want because it would have duplicate data, however, it does mean less joins.
This question already has answers here:
EntityType has no key defined error
(13 answers)
Closed 6 years ago.
Developing a basic ASP.net MVC 4 application. Its a simple product catalog application, where in I have 2 database tables ('Category' and 'Products')
There is a foreign key reference of 'Category id' (primary key in Category table) in 'Products' table.
When I run the application, I am getting error message (listed below).
System.Data.Entity.Edm.EdmEntityType: : EntityType 'Category' has no key defined. Define the key for this EntityType.
System.Data.Entity.Edm.EdmEntitySet: EntityType: EntitySet 'Category' is based on type 'Category' that has no keys defined
This looks like a common error for newbies,I did check all the related solutions to 'Entity key '' has no key defined.' but still my problem is not solved, Kindly help me in understanding this problem and what is the correct solution to this problem.
Below are my model classes
Category.cs
namespace ChemicalStore.Models
{
public partial class Category
{
public int CatId { get; set; }
public string CatName { get; set; }
public string CatDescription { get; set; }
public List<Product> Product { get; set; }
}
}
Products.cs
namespace ChemicalStore.Models
{
public class Product
{
public int ProductId { get; set; }
public int CatId { get; set; }
public string ProductTitle { get; set; }
public string ProductPrice { get; set; }
public string ProductDescription { get; set; }
public string ProductPackage { get; set; }
}
}
You should add attribute [Key] before property CatId:
using System.ComponentModel.DataAnnotations;
public partial class Category
{
[Key]
public int CatId { get; set; }
public string CatName { get; set; }
public string CatDescription { get; set; }
public List<Product> Product { get; set; }
}
The problem is that EF can work only when it knows primary key of table. By default EF recognize as primary key property with name Id. If your table has another primary key, you can mark it with attribute [Key] or set Key with fluent configuration.
Entity Framework uses a primary key field to create the primary key column on the generated table.
It uses convention to get this column with some variations:
If the field is called id or any casing variance;
If the field is called ClassNameId of any casing variance;
I may be missing some more conventions, but these are the most common cases.
If you don't have any field with this conventions you need to mark your desired primary key with the attribute [Key]:
[Key]
public int CatId { get; set; }
I was able to solve this by adding a setter to my key property; I only had a getter before.
public int Id { get; set; }
Just place [key] attribute on above id ..
[Table("employee")]
public class Employee
{
[Key]
public int Empno { set; get; }
public string Empname { set; get; }
}
Entity classes are auto generated..
Manual changes to those files will be overwritten if the code is regenerated.
You need to create a partial class with all your metadata
[MetadataType(typeof(Category.CategoryMetadata))]
public partial class Category
{
internal sealed class CategoryMetadata
{
[Key]
public int CatId { get; set; }
[Required]
public string CatName { get; set; }
public string CatDescription { get; set; }
public List<Product> Product { get; set; }
}
}
Read more on MSDN
Hi if you are getting below error.
""One or more validation errors were detected during model generation:
Checking.Models.Employee: : EntityType 'Employee' has no key defined. Define the key for this EntityType.""
just check your table column name and defined property name same or not .
if not then correct it proble resolved.
In my case I fixed this problem adding the right connectionString in the web.config/app.config file.
I had forgotten adding it and the DBContext was not able to communicate with the DB.
Hope it helps
I am having a hard time solving the following with an MVC view.
My goal is to display data from multiple tables in a single MVC view. The bulk of the data comes from a table called Retailers. I also have another table called RetailerCategories which stores the retailerid from the Retailers table and also a categoryid linking to a Category table.
Note that there are multiple records for each retailerid in the RetailerCategories table.
In the view I want to show a list of retailers and with each retailer I want to show the list of categories applicable to them.
What would be the best way to accomplish this? Some of the things I have tried are covered in Can you help with this MVC ViewModel issue?
This however does not appear to be the right approach.
You need a view model specifically tailored to the needs of this view. When defining your view models you shouldn't be thinking in terms of tables. SQL tables have absolutely no meaning in a view. Think in terms of what information you need to show and define your view models accordingly. Then you could use AutoMapper to convert between your real models and the view model you have defined.
So forget about all you said about tables and focus on the following sentence:
In the view I want to show a list of
retailers and with each retailer I
want to show the list of categories
applicable to them.
This sentence is actually very good as it explains exactly what you need. So once you know what you need go ahead and modelize it:
public class CategoryViewModel
{
public string Name { get; set; }
}
public class RetailerViewModel
{
public IEnumerable<CategoryViewModel> Categories { get; set; }
}
Now you strongly type your view to IEnumerable<RetailerViewModel>. From here it is easy-peasy to do what you want in the view:
showing a list of retailers with each retail having a list of associated categories.
this could be also helpful;
video from chris pels
It is simple just do what I say step by step.
add connection string into web.config file
select models from solution explorer and add 4 classes as following
1st class for first table "i have employ table which have 3 columns
public class Employ
{
[Key]
public int Emp_id { get; set; }
public string Emp_name { get; set; }
public string Emp_city { get; set; }
}
2nd class for my tempo table
public class tempo
{
[Key]
public int ID { get; set; }
public int Emp_Id { get; set; }
public string subject { get; set; }
public string hobby { get; set; }
}
Now I create a third class in model folder which contain value that i want from employ table and tempo table
public class Alladd
{
public int ID { get; set; }
public int Emp_Id { get; set; }
public string subject { get; set; }
public string hobby { get; set; }
public string Emp_name { get; set; }
public string Emp_city { get; set; }
}
and the final class is datacontext class
public class DataContext:DbContext
{
public DataContext() : base("DefaultConn")//connection string
{
}
public DbSet<Employ> Empdata { get; set; }
public DbSet<tempo> Tempdata { get; set; }
}
now go to the Home controller and add code as below
public ActionResult file()
{
// IList<tempo> tempi=new List<tempo>();
IEnumerable<Alladd> model = null;
// model = getVerifydetails(id);
// return View(objcpModel);
List<Alladd> verify = new List<Alladd>();
cn.Open();
if (cn.State == ConnectionState.Open)
{
string query = "select Employ.Emp_name,Employ.Emp_id,Employ.Emp_city,tempo.hobby,tempo.id,tempo.subject from Employ inner join tempo on Employ.Emp_id=tempo.Emp_id;";//joining two table
SqlCommand cmd=new SqlCommand(query,cn);
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
verify.Add(new Alladd { Emp_name = dr[0].ToString(), Emp_Id= Convert.ToInt32(dr[1].ToString()), Emp_city = dr[2].ToString(), hobby = dr[3].ToString(),ID = Convert.ToInt32(dr[1].ToString()),subject= dr[4].ToString()});//filling values into Alladd class
}
cn.Close();
}
return View(verify);
}
now the final step is so simple
go to solution explorer
select views folder and left click on it and select add view
now name it as "file" which we give it into controller
check on create strongly type view
select model class from dropdown-> Alladd
select scaffold templet ->List
hit Add button
Now you're done
Happy coding...
i'd like to know, I have a application in asp.net mvc and nhibernate. I've read about that in the Views on asp.net mvc, shouldn't know about the Domain, and it need use a DTO object. So, I'm trying to do this, I found the AutoMapper component and I don't know the correct way to do my DTOS, for some domain objects. I have a domain class like this:
public class Entity
{
public virtual int Id { get; set; }
public virtual bool Active { get; set; }
}
public class Category : Entity
{
public virtual string Name { get; set; }
public virtual IList<Product> Products { get; set; }
public Category() { }
}
public class Product : Entity
{
public virtual string Name { get; set; }
public virtual string Details { get; set; }
public virtual decimal Prince { get; set; }
public virtual int Stock { get; set; }
public virtual Category Category { get; set; }
public virtual Supplier Supplier { get; set; }
public Product() { }
}
public class Supplier : Entity
{
public virtual string Name { get; set; }
public virtual IList<Product> Products { get; set; }
public Supplier() { }
}
I'd like to get some example of how can I do my DTOs to View ? Need I use only strings in DTO ? And my controllers, it should get a domain object or a DTO and transform it on a domain to save in repository ?
Thanks a lot!
Cheers
There is no guidelines on this matter and it depends on your personal chice. I have few advices that have proven useful in practice:
1. Use flat DTOs - this means that the properties of the DTO must be as primitive as possible. This saves you the need for null reference checking.
For example if you have a domain object like this:
public class Employee
{
prop string FirstName{get; set;}
prop string LastName{get; set;}
prop Employee Boss{get; set;}
...
}
And you need to output in a grid a list of employees and display information for their 1st level boss I prefer to create a DTO
public class EmployeeDTO
{
prop string FirstName{get; set;}
prop string LastName{get; set;}
prop bool HaveABoss{get;set}
prop string BossFirstName{get; set;}
prop string BossLastName{get; set;}
...
}
or something like this (-:
2. Do not convert everything to sting - this will bind the DTO to a concrete view because you'll apply special formatting. It's not a problem to apply simple formatting directly in the view.
3. Use DTOs in your post actions and than convert them to domain objects. Usually controller's actions are the first line of deffence against incorrect data and you cannot expect to be able to allways construct a valid domain object out of the user's input. In most cases you have to do some post-processing like validation, setting default values and so on. After that you can create your DTOs.